There is disclosed at method for conducting a reaction, which is characterised in that carbon dioxide is combined with an alkaline solution based on ammonia, for the formation of ammonium bicarbonates, said bicarbonates being further reacted with a saline comprising solution, forming products of alkaline metal bicarbonate and ammonium chloride, and said ammonium chloride product is processed further in a decomposition to form ammonia and hydro chloric acid, and said ammonia chloride is returned to the first step forming said alkaline solution with water, while the alkaline metal bicarbonate is optionally further decomposed into carbon dioxide which is returned to the first step of the method. According to another aspect, the invention is used for handling of brine water originating from a desalination plant, for removing carbon dioxide from combustion gas, such as related to power plants or other industrial activities. Preferably the method is used in a combined process for removing carbon dioxide from combustion gas and desalination of water.